Wake Turbulence Research Modeling

Wake Turbulence Research Modeling John Shortle, Lance Sherry Jianfeng Wang, Yimin Zhang George Mason University C. Doug Swol and Antonio Trani Virginia Tech

Introduction This presentation and a companion presentation from MIT examine the NextGen Concept of Operations to determine what parts (if any) of the concept may cause an increased risk of an aircraft encountering a wake turbulence hazard over today s operations Identification of these potential risk areas will help the FAA focus efforts towards a more refined risk assessment and development of any necessary mitigation strategies The main focus of the research work presented is the development of tools (i.e., computer models) to study potential wake turbulence hazards in future NextGen procedures Our thanks to Ed Johnson, Tom Proeschel, Steve Lang and Jeff Tittsworth for supporting this project 2

NEXTOR Research Tasks Task 1 Examine the NextGen Concept of Operations and determine what parts (if any) of the concept may cause an increased risk of an aircraft encountering a wake turbulence hazard over today s operations Task 2 Research questions, mitigations, and prioritization of wake hazards Task 3 Develop model of current operations for use as a modeling baseline in studies of future NextGen era operations Task 4 Assessment of relative wake turbulence encounter probability associated with NextGen scenarios 3

Modeling Outline VT GMU / VT 1. Airport and Date Selection (Cluster Analysis) 2. PDARS Data Analysis GMU 4. Wake Area Model (TDAWP) GMU 3. Baseline Analysis, Rigid Wake Area 5. Baseline Analysis, Dynamic Wake Area VT GMU 6. NextGen CONOPS Procedures and Modeling MIT VT 7. NextGen Analysis, Rigid Wake Area 8. NextGen Analysis, Dynamic Wake Area 4

Radar Flight Track Data Airport Selection Selected ATL, LAX and NYC Busy terminal airspaces, diversity of aircraft types Potential interaction between multiple airports in terminal area Cluster analysis to select representative days (2008 as baseline year) Seven days of data for each airport IMC/MMC/VMC days Performance Data Analysis & Reporting System (PDARS) Aircraft position, velocity, altitude, heading Required parsing and data scrubbing Airport and Date Selection Historic Flight Track Data 5

Sample Flight Tracks, LAX Area Do these tracks contain clues for types of trajectory interactions that may lead to increased exposure to wake turbulence under NextGen? 6 6

First Order Analysis and Modeling 8

First Order Approach Objective: Identify types of potential NextGen trajectories that may increase the potential for wake turbulence encounters from analysis of existing complex / interacting trajectories Define region of space that is likely to contain the wake Note: Inside the region does not imply a wake encounter Geometry of region is simple Assumed to be rigid with fixed dimensions (parametric analysis) Many factors ignored in first order approach (wind, aircraft weight, etc.) Size of the region is selected by the user based on appropriate wake characteristics 9

Approach Summary Identify scenarios where one airplane passes through the zone of another Only consider cases in which the wake generating aircraft is Large, B757, or Heavy (ignore small and unknown) Visually check each scenario using Google Earth Identify themes determine if similar themes could be likely in NextGen era operations Conclusions are qualitative Approach is deliberately pessimistic Identify a wide set of potential NextGen scenarios Narrow set with more refined analysis Analyze narrowed set of scenarios for potential increased wake encounter probability assuming NextGen era separations and operational concepts 10

Development of Tools & Methods The following examples illustrate development of analysis tools & methods using existing radar tracks NextGen aircraft trajectories will be synthesized based on capabilities likely to be operational in a time period of interest A positive result indicates the potential for a wake encounter based on parameters chosen by the modeler A potential encounter may be nearly indistinguishable from background turbulence Both the track data and the preliminary wake models contain known uncertainties Identifying potential for wake encounters under NextGen operations rather than analyzing specific events in detail There are: NO known wake encounters in any of these cases NO known deviations from required separations in any of these cases These examples do not indicate any areas of concern in the NAS 11

Example Departing SNA 12 12

EWR Arrivals / TEB Operations Arrival / departure from TEB under arrival to EWR 13

JFK Parallel Turns 22L / 22R approach on turn 14

Turns on Approach (ATL) Approach to Same Runway Parallel Approach 15

Crossing Arrivals and Departures Departures Arrivals 16

Summary Scenarios from Original Brainstorm Session Scenario Arrivals Same runway Merging of arrival streams Turns to parallel approaches Crossing arrivals and departures Departures Other Potential Wake Turbulence Scenarios Identified GA aircraft flying under arrivals Holding patterns Irregular operations 17

Wake Area Model Describe wake area as 3D polyhedron (currently 2D) Polyhedron is a function of: Aircraft: Velocity, mass, wingspan, altitude Atmosphere: Eddy dissipation rate, Brunt Vaisala frequency, air density, wind speed/direction Circulation threshold (t 1, z+ 1 ) (t 2, z+ 2 ) (t 3, z+ 3 ) (t 1, z- 1 ) (t 2, z- 2 ) (t 3, z- 3 ) 19

Example Wake Area ε*=[0,.1], N* = [0,.1], Γ* =.1 2 0 Normalized Relative Vertical Position (unitless) -2-4 -6 Coordinates of area stored in lookup table -8-10 -12-14 0 5 10 15 20 25 30 35 40 45 Normalized Time (unitless) TDAWP model, GMU implementation based on Proctor, Hamilton, 20 Swizter, 2006, TASS driven algorithms for wake prediction. 20

Dynamic Wake Envelope Modeling 21

Wake Encounter Model (WEM) A Model to Identify Potential Wake Encounters with Dynamic Wake Area Dynamic wake area model WEM flies each aircraft along its radar (or prescribed) track using a step size of 5 seconds WEM tests whether aircraft has the potential to encounter a wake envelope of surrounding aircraft WEM produces a series of outputs: Potential wake encounters for given day/terminal area Potential encounters by aircraft type Potential encounters by location Potential encounters under differing atmospheric conditions Aggregate counts of potential encounters (compared to today) will be used to identify NextGen operational concepts requiring further research 23

Important Points About the Analysis A potential wake vortex encounter as determined from these models does not represent a real wake vortex encounter (e.g., unsafe conditions in the system) The assumed values of circulation strength, BVF and EDR parameters are set to very low values and were not present in the atmosphere during the days of analysis The potential wake vortex interactions were not reported in the NASA ASRS database A potential wake vortex encounter merely implies that under optimal atmospheric conditions, an aircraft generating a wake could produce a wake that could impinge on another aircraft 24

NYC Results: IMC Five potential wake encounters during an IMC day Arriving EWR flights create potential wake vortex interactions with departing TEB flights Date Weather Condition 3/19/2008 IMC Circulation Threshold EDR BVF Potential Wake Encounters Flights 75 0.0001 0.0005 5 4,765 75 0.0020 0.0100 2 4,765 75 0.0040 0.0200 1 4,765 125 0.0001 0.0005 4 4,765 125 0.0020 0.0100 1 4,765 125 0.0040 0.0200 0 4,765 175 0.0001 0.0005 3 4,765 175 0.0020 0.0100 0 4,765 175 0.0040 0.0200 0 4,765 Circulation strength threshold expressed in m 2 /s, EDR in m 2 /s 3 and BVF in 1/s 25

New York Results: IMC Flight Path for TEB Departures X Potential Wake Encounters Flight Path for EWR Arrivals 26

WEM Model Results (LAX) IMC LAX had two potential wake encounters (1 IMC, 1 VMC) Both were departure interactions IMC encounter details: Wake produced by Embraer 190 (Large) Potential wake encountered by Embraer 120 (Small) Date Weather Condition 7/18/2008 IMC Circulation Threshold EDR BVF Potential Wake Encounters Flights 75 0.0001 0.0005 1 5,453 75 0.0020 0.0100 0 5,453 75 0.0040 0.0200 0 5,453 125 0.0001 0.0005 0 5,453 125 0.0020 0.0100 0 5,453 125 0.0040 0.0200 0 5,453 175 0.0001 0.0005 0 5,453 175 0.0020 0.0100 0 5,453 175 0.0040 0.0200 0 5,453 Circulation strength threshold expressed in m 2 /s, EDR in m 2 /s 3 and BVF in 1/s 27

LAX Results: VMC Wake Produced by Boeing 777 200 (Heavy) Affected aircraft: Embraer 135 (Large) Aircraft taking off from parallel runway Date Weather Condition 6/18/2008 VMC Circulation Threshold EDR BVF Potential Wake Encounters Flights 75 0.0001 0.0005 1 5,380 75 0.002 0.01 0 5,380 75 0.004 0.02 0 5,380 125 0.0001 0.0005 1 5,380 125 0.002 0.01 0 5,380 125 0.004 0.02 0 5,380 175 0.0001 0.0005 1 5,380 175 0.002 0.01 0 5,380 175 0.004 0.02 0 5,380 Circulation strength threshold expressed in m 2 /s, EDR in m 2 /s 3 and BVF in 1/s Potential Wake Encounter X Flight Track of Boeing 777 200 28

Potential Encounters by Wake Category and Weather Conditions Most potential wake encounters produced by large aircraft Large aircraft are more common than heavy aircraft at the airports studied Wake Generator Wake Encounterer Potential Number of Encounters Heavy Large 2 757 Small 1 Large Large 1 Large Small 6 Most potential encounters occurred during IMC which was surprising Skewed result since most IMC potential encounters associated with EWR/TEB scenario Weather Condition Potential Number of Encounters IMC 6 MMC 2 VMC 2 29

Preliminary Conclusions Two modeling approaches to identify potential wake issues in NextGen have been presented: First-order model (fixed wake area) Dynamic wake model Models are sensitive to input variables (EDR, BVF, circulation strength, aircraft state, etc.) Models can study thousands of flights to identify areas of potential wake encounters or interactions Models will offer insight to assess the relative wake turbulence encounter probability associated with NextGen scenarios 30

Future Research Analyze more data (ATL, DCA, other) Continue analysis of NYC data Conclusions likely qualitative with only single days of data Improvements to wake area models Lateral component of wake profiles (wind and turning effects Non uniform spacing of parameter intervals Inclusion of uncertainty Continue development of wake encounter pointmodel Moving from using baseline to validate proper operation of the tool to NextGen analysis 31